Presently, great progress has been made in the field of magnetic recording media. A magnetic disc is widely used as magnetic recording media to store data in magnetizable form. Typically, the data stored on the magnetic disc or record data on the disc is read by a read-write head of the magnetic recording media. The read-write head is moved relative to the disc and selectively positioned at close proximity to the surface of the data storage region to perform "read" or "record" data operation. Namely, the read-write head is selectively positioned radially across the data storage region to either record or retrieve data that is located on the particular position on the disc. As is well known in the art, the distance between the bottom surface of the read-write head and the surface of the disc is referred to as the "flying height" of the read-write head. The closer the read-write head, the more data that can be stored on the disc. When the disc rotates near its operating speed, the read-write head is supported in parallel, spaced apart relation to the disc's surface by an "air bearing" that is formed by air flowing between the read-write head and the upper surface in the direction of disc rotation as the disc rotates. After the reading or recording operation and during deceleration of the disc, the arm of the read-write head is moved inward to position the glide head directly on the landing zone of the disc. Thus, the read-write head contacts the landing zone when the disc driver is stationary. Prior to the next reading or recording operation, the disc is accelerated from stationary on the disc by the disc driver. The arm is not actuated to remove the read-write head from the landing zone until the read-write head is supported by the "air bearing".
The demand for high recording density of the disc requires a continuous decrease in the head/disc spacing. It is well known that the disc surface topography has to be controlled for a low roughness so that the glide heads can fly safely at such low glide height without sacrificing the head/disc stiction. A smooth, specular recording surface is thus used, which permits closer proximity of the read-write head to the disc surface. However, if the surface of the disc is too flat, the precision match of the surface gives rise to excessive stiction and friction during the start-up and stopping of the disc. Therefore, the surface of the landing zone formed on the disc is intentionally roughened to induce the head/disc stiction. The increased surface roughness of the contact area is achieved by controlled texturing of the disc. Therefore, the landing zone is textured to a very tight range and well-defined topography.
FIG. 1 illustrates a typical data recording medium, i.e. a magnetic disc 2 and a glide head 4. The glide head 4 is used to detect the flying height of the disc 2. At the center of the magnetic disc 2 is an opening 10 to accommodate to a vertical spindle of a disc drive for rotating the disc 2. The upper surface of the disc 2 further includes a radially inward section 12 for clamping the disc with respect to the spindle. A landing zone 14 is formed on the surface of the disc 2. When the disc 2 is at rest, the glide head 4 is located in contact with the landing zone 14. Between the landing zone 14 and the outer circumferential edge 16 of the disc 2 is a data storage region 18 to store data.
Typically, one or more discs 2 are rotated on a central axis of a disc driver. Generally, the glide head 4 is radially moved relative to the disc 2 vertical to the arm 6 (the direction of movement is denoted by an arrow) and selectively positioned at close proximity to the surface of the data storage region 18 to detect the flight height. The flight height is controlled as close to the surface of the disc 2 as possible, i.e., to minimize the "flying" height of the glide head 4. When the disc rotates near its operation speed, the glide head 4 is supported by the "air bearing" as the disc 2 rotates. Thus, what is required is a method to determine the glide height of the textured disc.